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Biomedical subjects

R Snyder

Publications and source records attributed to R Snyder.

At least 91 records · Page 5Linked to original sources

Withdrawing life support--the survivors.

We studied the impact of withdrawal of life support on surviving relatives and families of patients who died when chronic dialysis was discontinued. Fifty-four (57%) relatives answered a written questionnaire. The relatives of 70% of home dialysis patients and 27% of center dialysis answered the questionnaire. The answering relative felt most angry and uncomfortable with the decision, ascribed the least anger and most comfort to the patient and an intermediate value to the rest of the family. Staff physician and resident ranked highest in involvement in making the decision, social workers and chaplains the lowest. Once the decision was made, social workers and nurses were most caring and helpful, residents and chaplains were rated the lowest. The relatives felt that they and the patients were the ones who most often brought up the decision to stop and also made the final decision. The relatives thought that the incompetent patients were most angry and uncomfortable but that they felt that decision to be right. The family and relatives were particularly angry and uncomfortable when the patient had discontinued dialysis for the stress of the procedure alone and not any medical complications. In these cases there was most family disagreement and the staff received startling low scores, both for involvement and caring and helpfulness. In answers to open-ended questions, the relatives expressed disappointment with physicians who were unwilling to talk to them, were overly optimistic and continued too long with treatment. They wished for more openness and truthfulness. No long-term psychological harm seems to have come to the relatives and families with one exception. Our finding suggests that more meetings with families and patients and openness about problems and complications during chronic dialysis and follow-up and counseling of families after the patients have died should be helpful.

Attitude to Death↗

Insulinlike growth factor II expression and oval cell proliferation associated with hepatocarcinogenesis in woodchuck hepatitis virus carriers.

Insulinlike growth factor II (IGF-II) is a highly mitogenic fetal growth factor suspected of regulating the growth of a wide spectrum of tissues via an autocrine or paracrine mode of action or both. High steady-state levels of IGF-II RNA were detected in 45% of hepatocellular carcinomas (HCCs) arising from woodchuck livers with persistent woodchuck hepatitis virus (WHV) infection. Analysis of WHV RNA in the same HCCs revealed that HCCs with high levels of IGF-II RNA contained low or undetectable levels of WHV RNA and HCCs with low levels of IGF-II RNA contained high levels of WHV RNA. Integrated WHV DNA was present in HCCs from both groups, but viral DNA replicating forms were present, predominantly in HCCs with low levels of IGF-II. Several IGF-II RNAs, the most prominent of which were poly(A) species of approximately 3.75 and 1.1 to 1.3 kilobases, were detected only in precancerous nodules and HCCs. Levels of IGF-II were elevated two- to three-fold in the serum of woodchucks with chronic active hepatitis preceding the occurrence of HCC. Proliferation of a population of oval cells, which arise from portal tract regions in the liver, preceded the development of HCC and was a prominent feature of livers from which tumors with high levels of IGF-II occurred. The HCCs tended to have distinct histological features according to their growth factor status. Tumors with low levels of IGF-II were generally highly differentiated acinar-trabecular HCCs, whereas tumors with high levels of IGF-II were more anaplastic, with regions of fibrosis and fatty accumulation. A model to relate the pathology of WHV infection to oval cell proliferation and IGF-II expression in the development of these heterogeneous HCCs is presented.

Animals↗

A prospective study of cisplatin-based combination chemotherapy in advanced germ cell malignancy: role of maintenance and long-term follow-up.

Two hundred fifty-three patients with advanced germ cell malignancy received initial chemotherapy with cisplatin, vinblastine, and bleomycin followed by surgical resection of residual masses if possible. Patients achieving complete remission (CR) were prospectively randomized to receive 6 months maintenance therapy with vinblastine or no further treatment. CR was achieved in 183 patients (72%) and a further eight patients (4%) had complete resection of residual viable malignancy (no evidence of disease [NED]). Pretreatment factors having a significant adverse influence on response by univariate analysis included extragonadal origin of the tumor, poor performance status, advanced lung or lung and abdominal disease, and elevated serum levels of human chorionic gonadotropin (HCG) and alpha-fetoprotein (AFP) greater than 1,000 ng/mL. Multivariate regression analysis indicated the independent prognostic factors of significance were advanced lung or advanced lung and abdominal disease, total tumor diameter greater than 10 cm, and a serum level of HCG greater than 1,000 ng/mL. Of the toxicities encountered, myelosuppression was significant, being exacerbated by radiotherapy, and seven deaths occurred from septicemia. Bleomycin pulmonary toxicity occurred in 46% of patients and was severe in 4%, resulting in eight deaths. With a median follow-up of 64 months, relapses have occurred in 25 patients with no significant difference between those patients receiving or not receiving maintenance vinblastine. Eight of these relapses occurred beyond 1 year and four beyond 2 years of follow-up. Presently, 68% of the total patient population is alive and disease-free, with 84% of the CR and NED patients alive and 81% alive and disease-free. It is concluded that with prolonged follow-up, vinblastine maintenance therapy does not improve treatment outcome. Moreover, late relapses occur, cautioning against premature pronouncements of cure.

Adolescent↗

Improving the quality of life during chemotherapy for advanced breast cancer. A comparison of intermittent and continuous treatment strategies.

Since chemotherapy for metastatic breast cancer is not curative, consideration of the quality of life is important in selecting a treatment regimen. We conducted a randomized trial comparing continuous chemotherapy, administered until disease progression was evident, with intermittent therapy, whereby treatment was stopped after three cycles and then repeated for three more cycles only when there was evidence of disease progression. Each approach was tested with doxorubicin combined with cyclophosphamide or with cyclophosphamide combined with methotrexate, fluorouracil, and prednisone. Intermittent therapy resulted in a significantly worse response (P = 0.02 by Mann-Whitney test), a significantly shorter time to disease progression (relative risk based on proportional-hazards model, 1.8; 95 percent confidence interval, 1.4 to 2.4), and a trend toward shorter survival (relative risk, 1.3; confidence interval, 0.99 to 1.6). The quality of life was expressed as linear-analogue self-assessment scores for physical well-being, mood, pain, and appetite and as a quality-of-life index. It improved significantly during the first three cycles, when all patients received treatment. Thereafter, intermittent therapy was associated with worse scores for physical well-being (by 23 percent of scale; 95 percent confidence interval, 11 to 35 percent), mood (25 percent; 13 to 37 percent), and appetite (12 percent; 0 to 24 percent) and for the quality-of-life index as indicated by the patient (14 percent; 5 to 23 percent) and the physician (16 percent; 7 to 26 percent). Changes in the quality of life were independent prognostic factors in proportional-hazards models of subsequent survival. We conclude that, as tested, continuous chemotherapy is better than intermittent chemotherapy for advanced breast cancer.

Antineoplastic Combined Chemotherapy Protocols↗

Formation of reactive metabolites from benzene.

Rat liver mitoplasts were incubated first with [3H]dGTP, to form DNA labeled in G, and then with [14C]benzene. The DNA was isolated and upon isopycnic density gradient centrifugation in CsCl yielded a single fraction of DNA labeled with both [3H] and [14C]. These data are consistent with the covalent binding of one or more metabolites of benzene to DNA. The DNA was enzymatically hydrolyzed to deoxynucleosides and chromatographed to reveal at least seven deoxyguanosine adducts. Further studies with labeled deoxyadenine revealed one adduct on deoxyadenine. [3H]Deoxyguanosine was reacted with [14C]hydroquinone or benzoquinone. The product was characterized using uv, fluorescence, mass and NMR spectroscopy. A proposed structure is described.

Animals↗

Monochloroacetic acid toxicity in the mouse associated with blood-brain barrier damage.

Monochloroacetic acid (MCA) causes front paw rigidity in 10% of mice surviving a single oral toxic dose (320-380 mg/kg). Mice exhibiting front paw rigidity were killed at various times after MCA treatment and their brains were prepared for histological examination. As early as 48 hr post-treatment, RBCs were found outside capillaries in several brain regions, especially the cerebellum. At time points up to 8 weeks after MCA, extracapillary RBCs were seen to be undergoing lysis, and there was loss of cerebellar Purkinje cells. Three hours after oral administration of an LD80 of MCA (380 mg/kg), entry of iv-injected [14C]inulin or [3H]dopamine (1.0 microCi) into all brain regions was significantly increased compared to controls. Increased entry of [14C]inulin into the brains of mice occurred as early as 2 hr after MCA, coinciding with the onset of signs of toxicity, and remained elevated for up to 8 hr following treatment. Further studies revealed that only those mice which were moribund but not those which were unaffected by MCA (380 mg/kg) 4-6 hr after treatment had significantly increased brain levels of [14C]inulin or [3H]dopamine. However, mice which survived an LD80 of MCA and exhibited front paw rigidity 24 hr later also had brain radiotracer concentrations significantly greater than controls. Both the lethal effects of MCA and the physical deficits observed in survivors may be associated with impairment of blood-brain barrier function.

Acetates↗

Phase I study of epirubicin given on a weekly schedule.

Epirubicin was studied in a phase I setting to find the maximum tolerated dose when given weekly for 3 of 4 weeks. Forty-one evaluable patients were treated in groups at doses increasing from 20 to 45 mg/m2. The highest dose level produced the maximum degree of myelosuppression (lowest neutrophil count, 1.9 X 10(9)/L; range, 0-3.7) recorded on Day 22. This was well-tolerated in this group of mainly pretreated patients. Nonhematologic side effects were minimal. This dose schedule allows a greater dose per unit time to be administered than other recommended schedules for epirubicin.

Adult↗

Antithyroid antibodies in Hispanic patients with type I diabetes mellitus. Prevalence and significance.

Antithyroglobulin antibodies (ATA) and antithyroid microsomal antibodies (AMA) were sought and thyroid function was determined in 90 Hispanic patients with type I diabetes mellitus followed up for up to seven years. We detected ATA in 7.5% of our patients and AMA in 34.8%. All serum samples positive for ATA also contained AMA. There was no sex difference in the prevalence of thyroid autoimmunity. A small, firm goiter was present in eight patients, one of whom developed Graves' disease. Our results suggest that a relatively high prevalence of AMA and no sex difference in thyroid autoimmunity may be unique features of Hispanic children and adolescents with type I diabetes mellitus. Such patients should be clinically evaluated for thyroid dysfunction and should be screened annually for the presence of AMA. When antibodies are present, laboratory evaluation of thyroid function should be performed frequently.

Adolescent↗

Metabolism of benzene and phenol in macrophages in vitro and the inhibition of RNA synthesis by benzene metabolites.

Benzene may affect hemopoiesis by damaging the bone marrow stroma that provides the microenvironment for hemopoiesis. A possible target of benzene toxicity in the stroma is the macrophage, which is a major source of protein factors required for the proliferation and differentiation of progenitor cells. As an initial approach towards understanding whether benzene inhibits hemopoietic factor production in bone marrow stroma, the metabolism of benzene and phenol has been studied and the effect of benzene and its metabolites on macrophage RNA synthesis has been examined. Benzene is not metabolized in macrophages but phenol, the major metabolite of benzene in bone marrow, is converted by peroxidase in the macrophage to both free metabolites and species which covalently bind to cellular macromolecules. Benzene and its metabolites inhibited RNA synthesis in a dose-dependent manner, with 50% inhibitory concentrations of 5 X 10(-3) M for benzene, 2.5 X 10(-3) M for phenol, 2.5 X 10(-5) M for hydroquinone, and 6 X 10(-6) M for p-benzoquinone; this inhibition was not attributable to loss of cell viability. Benzene, possibly by an inhibition of uridine transport into macrophages, and phenol, by its conversion to covalently binding species, inhibit RNA synthesis in macrophages and thus may inhibit the synthesis of colony stimulating factors required for hemopoiesis.

Animals↗

Vascular prosthesis standards: a manufacturer's viewpoint.

A review of the state of current commercial vascular grafts and the types of tests proposed by the Association for the Advancement of Medical Instrumentation Vascular Prosthesis Draft Standard is presented. The philosophy of the standard and the types of products covered are discussed. Several areas requiring additional development are noted. The status and future of the standard are now up to the general user community.

Biocompatible Materials↗

Amelioration of cisplatin-induced ototoxicity by fosfomycin.

The continued chemotherapeutic application of cisplatin (cis-diamminedichloroplatinum [II]) necessitates reduction of its dose-limiting toxicity without decreasing its tumoricidal effect. This research project evaluated the efficacy of fosfomycin, a phosphonic acid antibiotic, in decreasing or ameliorating the ototoxicity (high frequency sensorineural hearing loss) and nephrotoxicity (renal tubular necrosis and interstitial nephritis) of cisplatin. Experimentally, fosfomycin effectively inhibits aminoglycoside-induced ototoxicity and nephrotoxicity in animals and humans. The efficacy of fosfomycin in blocking platinum-induced toxicity in the guinea pig was evaluated histologically and functionally using cytocochleography and light microscopy of the organ of Corti and the auditory brain stem evoked response (ABR), and light microscopy of renal corticomedullary tissues, small bowel, liver, lung, and peripheral nerve. The results demonstrate that fosfomycin ameliorates the acute renal tubular necrosis and interstitial nephritis and markedly inhibits the elevation of ABR thresholds and simultaneous outer hair cell loss that can result from cisplatinum administration. Fosfomycin should be considered a potential antidote for the dose-limiting ototoxicity and nephrotoxicity of cisplatin chemotherapy.

Acute Kidney Injury↗